The former head of the RSPCA in Tasmania has withdrawn his unfair dismissal complaint after deciding he did not want to return to the post.

Ben Sturges lodged the application with Fair Work Australia after his sacking last November, prompted by an internal investigation into his conduct.

He was seeking to be re-instated, but yesterday revealed he had withdrawn his complaint.

Mr Sturges says he no longer wants to work with the organisation.

"While I still care very much about animal welfare in Tasmania, I believe that so much has happened with this organisation that it has essentially been gutted and I just feel that I could no longer go back and work for that organisation," he said.

The organisation's president Paul Swaitkowski has defended the body.

"There has been an immense amount of misinformation spread by various parties about the RSPCA to bring the organisation into disrepute," he said.

"The RSPCA relies on its credibility to do the neccessary thing it needs to do."

Free trade is the oldest argument in federal politics and the issue that literally defined the federation era but opposition exists to the TPP, courtesy of the Investor-State Dispute Resolutions clause.